Dual inductor circuit for multi-band wireless communication device

ABSTRACT

This disclosure describes a dual inductor circuit, which may be particularly useful in a mixer of a wireless communication device to allow the mixer to operate for two different frequency bands. The dual inductor circuit comprises an inductor-within-inductor design in which a small inductor is disposed within a large inductor. The two inductors may share a ground terminal, but are otherwise physically separated and independent from one another. Terminals of the inner inductor, for example, are not tapped from the outer inductor, which can reduce parasitic effects and electromagnetic interference relative to tapped inductor designs. The independence of the inductors also allows the different inductors to define different resonance frequencies, which is desirable.

This application claims the benefit of U.S. Provisional Application No.60/834,129, filed Jul. 28, 2006, the entire content of which isincorporated herein by reference.

FIELD

This disclosure relates to inductors that can be implemented withinwireless communication devices, and more particularly on-chip inductorcircuits used in wireless communication devices.

BACKGROUND

Inductors are common electrical circuit elements implemented withinwireless communication devices and a wide range of other electronicdevices. Although inductors are very useful and desirable, they areoften one of the most space-consuming elements of a radio frequencyintegrated circuit (RFIC). In an RFIC, inductors are commonly usedwithin amplifier elements of the RFIC component commonly referred to asthe “mixer.” A mixer generally refers to the portion of an RFIC whichgenerates (i.e., mixes) a baseband signal from a received carrierwaveform. Mixers are also used on the transmitter side, e.g., tomodulate a baseband signal onto a carrier.

On the receiver side, the mixer receives a waveform, which typicallyincludes a carrier wave modulated with a baseband data signal. The mixermay include an amplifier element to properly tune the received waveform.The mixer synthesizes a copy of the carrier wave, e.g., using a localoscillator (LO) of the device. The mixer then removes the basebandsignal from the received waveform by essentially subtracting the carrierwave generated by the LO from the received waveform. Once removed fromthe carrier, the baseband signal can then be converted into digitalsamples and demodulated, e.g., by a digital circuit.

An inductor may be used within the amplifier element of the mixer inorder to set the performance of the mixer to a particular operatingfrequency. Some wireless communication devices support multiplefrequency bands, in which case, multiple mixers are typically needed.Moreover, each mixer requires its own inductor to set its performance atthe operation frequency associated with the respective mixer. The use ofseveral different mixers to support multiple frequency bands isundesirable, particularly due to the space consumption that would berequired within the RFIC to accommodate the different inductors.

SUMMARY

In general, this disclosure describes a dual inductor circuit, which maybe particularly useful in a mixer of a wireless communication device toallow the mixer to operate for different frequency bands. The dualinductor circuit comprises an inductor-within-inductor design in which asmall inductor is disposed within a large inductor. The two inductorsmay share a ground terminal, but are otherwise physically separated andindependent from one another. Terminals of the inner inductor, forexample, are not tapped from the outer inductor, which can reduceparasitic effects and electromagnetic interference relative to tappedinductor designs. The independence of the inductors also allows thedifferent inductors to define different resonance frequencies, which ishighly desirable.

In one aspect, this disclosure provides a multi-band wirelesscommunication device comprising a mixer that mixes baseband signals fromreceived signals. The mixer comprises a dual inductor circuit includinga first inductor defining a first terminal and a second terminal,wherein the first inductor coils from the first and second terminals toa ground terminal. The dual inductor circuit also includes a secondinductor disposed inside the first inductor, the second inductordefining a third terminal and a fourth terminal, wherein the secondinductor coils from the third and fourth terminals to the groundterminal, and wherein third and fourth terminals of the second inductorare independent from the first inductor.

In another aspect, this disclosure provides a dual inductor circuitcomprising a first inductor defining a first terminal and a secondterminal, wherein the first inductor coils from the first and secondterminals to a ground terminal, and a second inductor disposed insidethe first inductor, the second inductor defining a third terminal and afourth terminal, wherein the second inductor coils from the third andfourth terminals to the ground terminal, and wherein third and fourthterminals of the second inductor are independent from the firstinductor.

In another aspect, this disclosure provides a method comprising mixingreceived wireless signals to baseband signals using a selected inductorof a dual inductor circuit in a wireless communication device, the dualinductor circuit including a first inductor defining a first terminaland a second terminal, wherein the first inductor coils from the firstand second terminals to a ground terminal, and a second inductordisposed inside the first inductor, the second inductor defining a thirdterminal and a fourth terminal, wherein the second inductor coils fromthe third and fourth terminals to the ground terminal, and wherein thirdand fourth terminals of the second inductor are independent from thefirst inductor.

In an added example, this disclosure provides a multi-band wirelesscommunication device comprising a mixer that mixes baseband signals ontoa carrier. The mixer comprises a dual inductor circuit including a firstinductor defining a first terminal and a second terminal, wherein thefirst inductor coils from the first and second terminals to a groundterminal, and a second inductor disposed inside the first inductor, thesecond inductor defining a third terminal and a fourth terminal, whereinthe second inductor coils from the third and fourth terminals to theground terminal, and wherein third and fourth terminals of the secondinductor are independent from the first inductor.

Additional details of various examples are set forth in the accompanyingdrawings and the description below. Other features, objects andadvantages will become apparent from the description and drawings, andfrom the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a multi-band wireless communication deviceaccording to an example of this disclosure.

FIG. 2 is a block diagram of a mixer suitable for incorporation in thewireless communication device of FIG. 1 according to an example of thisdisclosure.

FIG. 3 is a more detailed example of one amplifier design that may usean inductor circuit of this disclosure.

FIG. 4 is a circuit layout diagram of an inductor circuit thatimplements a tapped configuration in which a small inner inductor istapped from a larger inductor.

FIGS. 5 and 6 are exemplary circuit layout diagrams of dual inductorcircuits that comprise an inductor independently disposed within largerinductor according to examples of this disclosure.

FIG. 7 is a flow diagram illustrating a method that may be executed by awireless communication device implementing a dual inductor circuit asdescribed herein.

DETAILED DESCRIPTION

This disclosure describes a dual inductor circuit, which may beparticularly useful in a mixer of a wireless communication device toallow the mixer to operate for two different frequency bands. The dualinductor circuit comprises an inductor-within-inductor design in which asmall inductor is disposed within a large inductor. The two inductorsmay share a ground terminal, but are otherwise physically separated andindependent from one another. Terminals of the inner inductor, forexample, are not tapped from the outer inductor, and this can reduceparasitic effects and electromagnetic interference relative to tappedinductor designs. The respective independence of the inductors alsoallows the different inductors to define different resonancefrequencies, which is desirable.

The maximum interference between both inductors occurs at eitherinductor's self resonant frequency. A tapped inductor's self resonantfrequency, however, is determined by the entire structure and notindividual inductor coils. In an application using a tapped inductor, itis possible that the self resonant frequency of the structure may occurnear the desired operating frequency of the inner coil. In such a case,performance of the circuit using the inner coil can be drasticallyimpacted.

In contrast to a tapped inductor design, the inductor-inside-inductortopology described herein may have two independent self resonantfrequencies, one for each independent inductor coil. The outer inductorcoil can have a lower self resonant frequency than the inner inductorcoil, and for some applications it is possible this resonant frequencycan approach the desired operating frequency of the inner inductor coil.In such a situation, impact to performance of the circuit using theinner inductor coil can be minimized due to isolation between the twodifferent inductor coils. Therefore, due to low coupling between bothinner and outer coils, two separate self resonant frequencies can exist,which can make the inductor-inside-inductor more desirable and canreduce or eliminate any negative impact on the performance of the innerinductor coil.

FIG. 1 is a block diagram of a multi-band wireless communication device10 according to an example of this disclosure. The block diagram of FIG.1 is simplified for purposes of explanation of the dual inductor circuitof this disclosure. Many other components (not illustrated) may also beused in device 10. Device 10 may comprise a cellular or satelliteradiotelephone, a radiotelephone base station, a computer that supportsone or more wireless networking standards, a wireless access point forwireless networking, a PCMCIA card incorporated within a portablecomputer, a direct two-way communication device, a personal digitalassistant (PDA) equipped with wireless communication capabilities, andthe like. These and many other types of devices may use the dualinductor circuit designs described herein.

Device 10 may implement one or more of a wide variety of wirelesscommunication standards or techniques. Examples of wirelesscommunication techniques include frequency division multiple access(FDMA), time division multiple access (TDMA) and various spread spectrumtechniques. One common spread spectrum technique used in wirelesscommunication is code division multiple access (CDMA) signal modulationin which multiple communications are simultaneously transmitted over aspread spectrum signal.

Furthermore, some wireless standards make use of two or more techniques,such as GSM systems, which use a combination of TDMA and FDMAmodulation. GSM stands for “Global System for Mobile Communications.” Anumber of wireless networking standards, and other wirelesscommunication standards and techniques have also been developed,including several IEEE 802.11 standards, Bluetooth standards, andemerging ultra-wideband (UWB) techniques and standards.

Device 10 may be referred to as “multi-band” insofar as it supportswireless communication in two or more wireless frequency bands. As anexample, device 10 may support CDMA or GSM wireless communication in onefrequency band, e.g., around 2.4 gigahertz (GHz), and may also supportlegacy analog wireless communication in another frequency band, e.g.,around 800 megahertz (MHz). As another example, device 10 may supportCDMA and/or GSM wireless communications in two different frequencybands, e.g., around 1.8 GHz and 2.4 GHz, respectively. The dual inductorcircuit designs described herein may help to support any two frequencybands, and may be used with a wide variety of wireless communications.The frequency bands and standards listed herein are merely exemplary.

Device 10 may comprise an analog receiver circuit 11 and a digitaldemodulation circuit 19. Analog receiver circuit 11 may comprise aso-called radio frequency integrated circuit (RFIC). Digitaldemodulation circuit 19 may comprise a digital modem(modulation-demodulator). Circuits 11 may be fabricated on separatechips or a common chip.

As illustrated, device 10 includes an antenna 12 that receives wirelesssignals. The wireless signals may be separated into different paths bysignal path separation circuit 13. Thus, the dual band design allows asingle antenna to receive two different signal frequencies, although inother cases, separate antennas could be used to receive the differentsignals at the different frequencies. In FIG. 1, for each signal path,the respective signal is scaled by a low noise amplifier (LNA) 14A or14B and delivered to mixer 15. Mixer 15 makes use of a dual inductorcircuit 16, as described herein, to allow the mixer to handle two ormore different frequency bands. In particular, dual inductor circuit 16may be implemented within an amplifier (not shown in FIG. 1) of mixer15. The amplifier of mixer 15 scales the wireless signals from arespective one of LNAs 14A or 14B and then mixes the signal to baseband.

The received wireless signal may comprise a carrier waveform modulatedwith a baseband signal. Mixer 15 removes the baseband signal from thecarrier of the received signal so that sampling and demodulation can beperformed on the baseband signal. In particular, mixer 15 may receive areference waveform produced by a local oscillator (not shown) of device10. Mixer 15 subtracts the reference waveform from the received wirelesssignal to remove the carrier and produce the baseband signal. Thebaseband signal is then filtered by one or more filters 17. Ananalog-to-digital (A/D) converter 18 converts the baseband signal intodigital baseband samples, which are forwarded to a digital demodulationcircuit 19 for demodulation.

Mixer 15 is a dual band mixer in that it supports two differentfrequency bands, e.g., a first signal in a first frequency band from LNA14A and a second signal in a second frequency band from LNA 14B. Device10 may operate in two different modes, which support wirelesscommunication at the two different frequency bands. These two modes maycomprise an analog and digital mode, two different digital modes, orpossibly two different analog modes. Dual inductor circuit 16 includestwo different independent inductors. One of the inductors (a smallercoil) is disposed inside the other inductor (a larger coil). In thismanner, dual inductor circuit 16 provides the ability to support twodifferent frequency bands, yet achieves a relatively compact andefficient two-dimensional circuit design.

Dual inductor circuit 16 may have reduced parasitics and electromagneticinterference relative to inductor circuits that employ a tapped inductorconfiguration. The two inductors of dual inductor circuit 16 may share aground terminal, but are otherwise physically separated and independentfrom one another. Unlike tapped inductor configurations, for example,terminals of the inner inductor of circuit 16 are not tapped from theouter inductor. This also allows the two inductors of dual inductorcircuit 16 to define different resonance frequencies.

The details of this disclosure primarily refer to a mixer on thereceiver side, e.g., that mixes baseband signals from a received signal.However, this disclosure also contemplates the use of the described dualinductor circuits in mixers on the transmitter side, e.g., thatmodulates a carrier with a baseband signal. Moreover, many otherdevices, including devices unrelated to wireless communication couldimplement the disclosed dual inductor circuits outlined in greaterdetail below.

FIG. 2 is a block diagram of a mixer 20 according to an example of thisdisclosure, which may correspond to mixer 15 of FIG. 1. As shown, mixer20 receives a wireless signal 21 that comprises a baseband signalmodulated on a carrier wave. Amplifier 22 is a tuning element thatconditions wireless signal 21 for mixing. Amplifier 22 includes a dualinductor circuit 25, as described in this disclosure, in order to allowmixer 20 to handle signals at two different frequency bands. A mode maybe selected, and based on the selected mode, dual inductor circuit 25may be set accordingly.

Mixing switcher 26 receives the wireless signal that is properly scaledby amplifier 22. Mixer switcher 26 also receives a reference waveformfrom frequency synthesizer 28. Frequency synthesizer 28 may access alocal oscillator (LO) 29 to generate the reference waveform at theexpected frequency. In order to support two different frequencies,frequency synthesizer 28 may implement adding techniques, subtractingtechniques, feed forward techniques, feed back techniques, or the like,to generate signals at different desired frequencies. Alternatively, twodifferent LO's could be used.

In any case, once a proper reference waveform is provided by frequencysynthesizer 28, mixer switcher 26 subtracts the reference waveform fromthe tuned wireless signal, which includes the carrier and the basebandsignal. In this manner, mixer 20 removes the carrier to generatebaseband signal 24. Baseband signal 24 can then be processed, possiblyconverted to digital samples, and then demodulated. In some cases,however, the demodulation could be done in an analog domain,particularly for legacy analog wireless formats or standards.

As described herein, mixer 20 supports at least two different frequencybands. In order to achieve such dual mode functionality in an efficientmanner, this disclosure provides dual inductor circuit 25. As describedin greater detail below, dual inductor circuit 25 comprises aninductor-within-inductor design in which a relatively small inductor isdisposed within a relatively large inductor. Again, the two inductorsmay share a ground terminal, but are otherwise physically separated andindependent from one another. Terminals of the inner inductor, forexample, are not tapped from the outer inductor, and this design canreduce parasitic effects and electromagnetic interference relative totapped inductor designs. This also allows the different inductors ofdual inductor circuit 25 to define different self resonance frequencies.

FIG. 3 is a more detailed example of one example of an amplifier 22Athat may use an inductor circuit of this disclosure. Amplifier 22A maycorrespond to amplifier 22 of FIG. 2. Amplifier 22A itself includes twodifferent amplifier circuits 23A and 23B, which operate with respect tothe different frequency bands. In particular, amplifier circuit 23A maybe used to scale signals in a cellular band and amplifier circuit 23Bmay be used to scale signals in a PCS band. Importantly, however, eachof amplifier circuits 23A and 23B couple to a common inductor circuit25A. Inductor circuit 25A employs an inductor-within-inductor design, asdescribe herein. An outer coil of inductor circuit 25A may be used toaccommodate cellular band signals scaled by amplifier circuit 23A and aninner coil of inductor circuit 25A may be used to accommodate PCSsignals scaled by amplifier circuit 23B.

Each duplicate amplifier circuit 23A and 23B is connected to theappropriate inductor terminals of inductor circuit 25A. The outputs ofeach duplicate amplifier circuit 23A and 23B are connected togetherbefore entering the mixer switcher 26 (FIG. 2). Control signals (“EnableCELL Band” and “Enable PCS Band”) may be used to select the appropriateamplifier at any given time. Enabling the cell band will disable the PCSband, and enabling the PCS band will disable the cell band.

FIG. 4 is a circuit layout diagram of an inductor circuit 30 thatimplements a tapped configuration in which a small inner inductor istapped from a larger inductor. Inductor circuit 30 is less desirablethan the other inductor circuits described herein because it uses onelarge coil from terminals 31 and 32 to ground terminal 35. A smallerinductor is created by tapping into the large inductor at anintermediate location, i.e. via terminals 33 and 34. The small inductorthat extends beyond these intermediate taps at terminals 33 and 34,however, adds substantial parasitic capacitance effects andinterference, which can substantially degrade the performance ofinductor circuit 30. In addition, because the smaller inductor is tappedfrom the larger inductor, the different inductors of inductor circuit 30typically have the same resonance frequency. The inductor designs shownin FIGS. 5 and 6 may overcome these or other shortcomings of theinductor circuit 30 of FIG. 4. Exemplary dimensions of inductor circuit30 are labeled.

FIGS. 5 and 6 are exemplary circuit layout diagrams of dual inductorcircuits 40 and 50 that comprise an inductor independently disposedwithin larger inductor, according to examples of this disclosure. Dualinductor circuits 40 and 50 may correspond to either of inductorcircuits 16 or 25 of FIGS. 1 and 2, or could be used in another type ofdevice. Unlike inductor circuit 30 in which the inner and outerinductors would have a common resonance frequency, the resonancefrequency of the different inductors of dual inductor circuits 40 and 50can be defined differently since the coils are independent. This ishighly desirable.

In particular, in contrast to a tapped inductor design, theinductor-inside-inductor topology shown in FIGS. 5 and 6 may have twoindependent self resonant frequencies, one for each independent inductorcoil. The outer inductor coil can have a lower self resonant frequencythan the inner inductor coil, and for some applications it is possiblethis resonant frequency can approach the desired operating frequency ofthe inner inductor coil. In such a situation, impact to performance ofthe circuit using the inner inductor coil can be minimized due toisolation between the two different inductor coils. Therefore, due tolow coupling between both inner and outer coils, two separate selfresonant frequencies can exist, which can make theinductor-inside-inductor more desirable and cause less negative impacton the performance of the inner inductor coil.

As shown in FIG. 5, dual inductor circuit 40 comprises a first inductor46 and a second inductor 48. The second inductor 48 is disposed insidefirst inductor 46. Both inductors 46 and 48 comprise coils that coil ina two-dimensional fashion. In this manner, circuit 40 defines aninductor-within-inductor design in which a small inductor coil (secondinductor 48) is disposed within a large inductor coil (first inductor46). For purposes of illustration, dimensions of dual inductor circuit40 are shown in FIG. 5. However, examples of this disclosure are notnecessarily limited to the sizes or shapes of the coils shown in FIG. 5.

First inductor 46 defines a first terminal 41 and a second terminal 42.First inductor 46 coils from the first and second terminals 41 and 42 toa ground terminal 45. Second inductor 48 is disposed inside firstinductor 46, but is independent from first inductor 46 and is not tappedfrom first inductor 46. In this manner, dual inductor circuit 40 isdifferent from inductor circuit 30 of FIG. 4, which employs a tappedconfiguration. In dual inductor circuit 40, second inductor 48 defines athird terminal 43 and a fourth terminal 44. Second inductor 48 coilsfrom third and fourth terminals 43 and 44 to ground terminal 45. Again,however, third and fourth terminals 43 and 44 of the second inductor 48are independent from the first inductor 46 insofar as third and fourthterminals 43 and 44 are not tapped from first inductor 46. Firstinductor 46 and second inductor 48 can be created to define differentresonance frequencies.

Dual inductor circuit 40 may be included within an amplifier of a mixerin order to allow the mixer to handle two different frequency bands.First inductor 46 may set the gain of the first frequency band andsecond inductor 48 may set the gain of a second frequency band.Moreover, using testing and simulations, first inductor 46 can be tunedto account for parasitic effects of second inductor 48, and secondinductor 48 can be tuned to account for parasitic effects of firstinductor 46. Since first and second inductors 46 and 48 are isolated(not tapped from one another), these parasitic effects and feedback aresignificantly reduced relative to a tapped configuration like that shownin FIG. 4.

First inductor 46 may be used in a first mode of operation of a wirelesscommunication device, and second inductor 48 may be used in a secondmode of operation of the wireless communication device. The first modeof operation may be associated with a first frequency band belowapproximately 1.0 gigahertz (GHz) and the second mode may be associatedwith a second frequency band above approximately 1.0 GHz. By way ofexample, the first frequency band may be a legacy analog band aroundapproximately 800 megahertz (MHz), and the second frequency band may bea band around approximately 2.4 GHz or 1.8 GHz. More generally, however,dual inductor circuit 40 could be tuned for any two frequency bands.

FIG. 6 is a circuit layout diagram providing another illustrativeexample of a dual inductor circuit 50 according to this disclosure. Dualinductor circuit 50 comprises a first inductor 56 and a second inductor58. Both inductors 56 and 58 comprise coils that coil in atwo-dimensional fashion. The two-dimensional layout of second inductor58 is disposed inside the two-dimensional layout of first inductor 56.Dimensions of dual inductor circuit 50 are shown in FIG. 6. However,examples of this disclosure are not necessarily limited to the sizes orshapes of the coils shown in FIG. 6.

In many respects, dual inductor circuit 50 of FIG. 6 is similar to dualinductor circuit 40 of FIG. 5. In particular, in dual inductor circuit50, first inductor 56 defines a first terminal 51 and a second terminal52, and first inductor 56 coils from the first and second terminals 51and 52 to a ground terminal 55. Second inductor 58 is disposed insidefirst inductor 56, but is independent from first inductor 56 and is nottapped from first inductor 56. In this manner, dual inductor circuit 50,like dual inductor circuit 40, is different from inductor circuit 30 ofFIG. 4, which defines a tapped configuration.

In dual inductor circuit 50, second inductor 58 defines a third terminal53 and a fourth terminal 54. Second inductor 58 coils from third andfourth terminals 53 and 54 to ground terminal 55. Third and fourthterminals 53 and 54 of the second inductor 58 are independent from thefirst inductor 56 insofar as third and fourth terminals 53 and 54 arenot tapped from first inductor 56. This also allows first inductor 56and second inductor 58 to be created to define different resonancefrequencies, which is highly desirable as described above.

Dual inductor circuit 50 may be included within an amplifier of a mixerin order to allow the mixer to handle two different frequency bands.First inductor 56 may be tuned to a first frequency band and secondinductor 58 may be tuned to a second frequency band. Moreover, usingsimulations and testing, first inductor 56 can be tuned to account forparasitic effects of second inductor 58, and second inductor 58 can betuned to account for parasitic effects of first inductor 56.

Dual inductor circuit 50 further reduces parasitic effects relative todual inductor circuit 40 due to more physical separation between firstinductor 56 and second inductor 58 compared to that between firstinductor 46 and second inductor 48 of dual inductor circuit 40. Inparticular, second inductor 58 may be separated from the first inductor56 by greater than approximately 20 microns. This can help to evenfurther reduce or eliminate electromagnetic interference and parasiticeffects between inductors 56 and 58. A surface area associated with dualinductor circuit 50 defines less than approximately 0.3 squaremillimeters, although this disclosure is not necessarily limited in thisrespect.

First and second inductors 56 and 58 are not only separated by greaterthan 20 microns of space, but are isolated (not tapped from oneanother). As discussed above, this isolation is also very useful inreducing parasitic effects and electromagnetic coupling effects betweeninductor 56 and 58. In particular, physical isolation of inductors 56and 58, in contrast to a tapped configuration, can significantly reduceparasitic capacitances and electromagnetic coupling between inductors 56and 58. In addition, this isolation allows inductors 56 and 58 to definedifferent resonance frequencies, which can avoid performance impacts forthe different frequency bands handled by the different inductors.

First inductor 56 may be used in a first mode of operation of a wirelesscommunication device, and second inductor 58 may be used in a secondmode of operation of the wireless communication device. The first modeof operation may be associated with a first frequency band belowapproximately 1.0 GHz and the second mode may be associated with asecond frequency band above approximately 1.0 GHz. As an illustrativeexample, the first frequency band may be a legacy analog band aroundapproximately 800 megahertz (MHz), and the second frequency band may bea PCS band around approximately 2.4 GHz or 1.8 GHz. More generally,however, dual inductor circuit 50 could be tuned for any two frequencybands. As an example, first inductor 56 may coil over a distance ofapproximately 0.35 to 0.6 millimeters, and second inductor 58 may coilover a distance of approximately 0.2 to 0.32 millimeters.

FIG. 7 is a flow diagram illustrating a method that may be executed by awireless communication device implementing a dual inductor circuit asdescribed herein. The functionality of FIG. 7 will be described withreference to wireless communication device 10 of FIG. 1. As shown inFIG. 7, device 10 selects a mode of operation (61), such as a digitalPCS mode that operates in a frequency band above 1.0 GHz, or an analog(or other mode) that operates in a frequency band below 1.0 GHz. Antenna12 receives a wireless signal (62), which includes a baseband signalmodulated onto a carrier wave. Depending on the mode of operation (63),inductor circuit 16 of mixer 15 selects either a first (outer) coil or asecond (inner) coil.

In particular, following scaling by one of LNAs 14A or 14B, the receivedsignal is passed to mixer 15. If device 10 is operating in a first modeof operation (“ONE” branch of 63), then mixer 15 uses a first inductorof inductor circuit 16 in the mixing process (64). Alternatively, ifdevice 10 is operating in a second mode of operation (“TWO” branch of63), then mixer 15 uses a second inductor of inductor circuit 16 in themixing process (65). As described herein, the second inductor isdisposed within the first inductor but includes independent terminalsthat are not tapped from the first inductor. A ground terminal may beshared by the first and second inductors. In this manner, mixer 15 cangenerate baseband signals for received signals associated with twodifferent frequency bands.

The baseband signals can be converted to digital samples (66) via A/Dconverter 18 and a digital demodulation circuit 19 can performdemodulation (67) with respect to the digital baseband samples. Ofcourse, the techniques of this disclosure can also work with purelyanalog signals, which would not be converted to digital samples, butwould be demodulated in the analog domain. In other words, one or bothof the modes of operation of device 10 could be a purely analog mode.

A number of examples have been described. The disclosedinductor-inside-inductor can be fabricated onto a radio frequencyintegrated circuit (RFIC), and may reduce the needed area and costsassociated with such RFIC fabrication. Although described with referenceto a mixer on an RFIC chip, the disclosed dual inductor circuit could beused in other devices. Also, the disclosed inductor could also be usedin a mixer of an RF transmitter that mixes baseband signals onto acarrier. Accordingly, these and other examples are within the scope ofthe following claims.

1. A multi-band wireless communication device comprising a mixer thatmixes baseband signals from received signals, the mixer comprising adual inductor circuit including: a first inductor defining a firstterminal and a second terminal, wherein the first inductor coils fromthe first and second terminals to a ground terminal; and a secondinductor disposed inside the first inductor, the second inductordefining a third terminal and a fourth terminal, wherein the secondinductor coils from the third and fourth terminals to the groundterminal, and wherein third and fourth terminals of the second inductorare independent from the first inductor.
 2. The device of claim 1,wherein the third and fourth terminals of the second inductor are nottapped from the first inductor.
 3. The device of claim 1, wherein thefirst inductor is tuned to a first frequency band and the secondinductor is tuned to a second frequency band.
 4. The device of claim 3,wherein the first inductor is tuned to account for parasitic effects ofthe second inductor and the second inductor is tuned to account forparasitic effects of the first inductor.
 5. The device of claim 1,wherein the second inductor is separated from the first inductor bygreater than approximately 20 microns.
 6. The device of claim 1, whereina surface area associated with the dual inductor circuit defines lessthan approximately 0.3 square millimeters.
 7. The device of claim 1,wherein the device supports a first mode of operation in which the mixerimplements the first inductor and a second mode of operation in whichthe mixer implements the second inductor.
 8. The device of claim 7,wherein the first mode is associated with a first frequency band belowapproximately 1.0 gigahertz (GHz) and the second mode is associated witha second frequency band above approximately 1.0 GHz.
 9. The device ofclaim 8, wherein the first frequency band is around approximately 800megahertz (MHz) and the second frequency band is around approximately2.4 GHz.
 10. The device of claim 1, wherein the mixer generates basebandsignals, the device further comprising: an analog-to-digital converterthat converts the baseband signals to digital baseband samples; and adigital demodulation circuit that demodulates the digital basebandsamples.
 11. The device of claim 1, wherein the dual inductor circuit isincluded in an amplifier of the mixer.
 12. The device of claim 1,wherein the first and second inductors have different resonancefrequencies.
 13. A method comprising mixing received wireless signals tobaseband signals using a selected inductor of a dual inductor circuit ina wireless communication device, the dual inductor circuit including: afirst inductor defining a first terminal and a second terminal, whereinthe first inductor coils from the first and second terminals to a groundterminal; and a second inductor disposed inside the first inductor, thesecond inductor defining a third terminal and a fourth terminal, whereinthe second inductor coils from the third and fourth terminals to theground terminal, and wherein third and fourth terminals of the secondinductor are independent from the first inductor.
 14. The method ofclaim 13, further comprising selecting between a first mode of operationin which a mixer implements the first inductor and a second mode ofoperation in which the mixer implements the second inductor.
 15. Themethod of claim 14, wherein the first mode is associated with a firstfrequency band below 1.0 approximately gigahertz (GHz) and the secondmode is associated with a second frequency band above approximately 1.0GHz.
 16. The method of claim 15, wherein the first frequency band isaround approximately 800 megahertz (MHz) and the second frequency bandis around approximately 2.4 GHz.
 17. The method of claim 13, furthercomprising: converting the baseband signals to a digital basebandsamples; and demodulating the digital baseband samples.
 18. The methodof claim 13, wherein the dual inductor circuit is included in anamplifier of a mixer of the wireless communication device.
 19. Themethod of claim 13, wherein the third and fourth terminals of the secondinductor are not tapped from the first inductor.
 20. The method of claim13, wherein the first inductor is tuned to a first frequency band andthe second inductor is tuned to a second frequency band.
 21. The methodof claim 20, wherein the first inductor is tuned to account forparasitic effects of the second inductor and the second inductor istuned to account for parasitic effects of the first inductor.
 22. Themethod of claim 13, wherein the second inductor is separated from thefirst inductor by greater than approximately 20 microns.
 23. The methodof claim 13, wherein a surface area associated with the dual inductorcircuit defines less than approximately 0.3 square millimeters.
 24. Themethod of claim 13, wherein the first and second inductors havedifferent resonance frequencies.
 25. A multi-band wireless communicationdevice comprising a mixer that mixes baseband signals onto a carrier,the mixer comprising a dual inductor circuit including: a first inductordefining a first terminal and a second terminal, wherein the firstinductor coils from the first and second terminals to a ground terminal;and a second inductor disposed inside the first inductor, the secondinductor defining a third terminal and a fourth terminal, wherein thesecond inductor coils from the third and fourth terminals to the groundterminal, and wherein third and fourth terminals of the second inductorare independent from the first inductor.